THE AMERICAN NATURALIST 



[Vol. XLIX 



5. Sexual reproduction and cross fertilization have 

 been advantageous in the evolution of organisms by limit- 

 ing cumulability and tlius confining the progress of the 

 group to a path bounded by the more permanent en- 

 vironment. 



6. Death occurs as a result of the continually forming 

 body cells becoming so variable through the absence of 

 control by amphimixis, that eventually some one group 

 fails to meet the limits imposed by the environment, and 

 these together with the remainder of the colony — the 

 in dividual — pe ri sh . 



3. Hypotheses 



The following opinions in the nature of hypotheses 

 based to a large extent on the preceding work may be 

 confirmed or invalidated by future investigations. 



1. Variability (cumulability) will be greater in a small 

 and isolated population than in a large and less isolated 

 population. 



2. Progressive evolution has resulted from factors aris- 

 ing through cumulations without reference to amphimuta- 

 tions (Mendclian combinations). 



3. Characters once established by cumulations produce 

 by fluctuations, amphimutations, etc., the diversity of 

 organic life. Such secondary variations are only in- 

 directly the products of evolution. 



BIBLIOGEAPHY 



Baitsell, G. A. 



'11. Conjugation of Closely Belated Individuals of Stylonychia. Pre 

 Soc. Exper. Biol, and Medicine, pp. 122-123. 



